Importance: Although it has been previously reported that the transition of extremely low-birth-weight survivors (≤1000 g) in their mid-20s was similar to that of normal-birth-weight controls (>2500g), there was uncertainty as to whether this positive pattern would persist. Objective: To compare the social functioning of low-birth-weight prematurely born adults aged 29 to 36 years with that of normal-birth-weight term controls. Design, setting, and participants: A population-based longitudinal cohort study was conducted in Ontario, Canada, between March 14, 2011, and August 13, 2013, among 100 of 165 low-birth-weight survivors (60.6%) prematurely born between January 1, 1977, and December 31, 1982, and 89 of 144 socio-demographically matched normal-birth-weight term controls (61.8%) recruited at age 8 years. Neurologic impairments were present in 20 premature participants (20.0%). Exposures: Extremely low birth weight. Main outcomes and measures: Information on health, educational level, employment, social integration, sexuality, and reproduction was obtained through standardized questionnaires completed by the participants. Results: Participants included 100 (39 males) extremely low-birth-weight survivors and 89 (33 males) normal-birth-weight term controls. The groups did not differ in the highest educational level achieved or in family and partner relationships. However, a lower proportion of premature adults was employed (odds ratio [OR], 0.37; 95% CI, 0.15 to 0.93) and fewer were employed full time (OR, 0.49; 95% CI, 0.24 to 0.98). The premature group had a mean total personal income of $20 000 less than controls, and more required social assistance (OR, 4.16; 95% CI, 1.13 to 15.33). Compared with the control group, more members of the premature group remained single (OR, 1.95; 95% CI, 1.08 to 3.50), had never had sexual intercourse (OR, 11.30; 95% CI, 2.56 to 49.91), did not have children (OR, 0.52; 95% CI, 0.27 to 0.99), reported more chronic health conditions (β, 1.54; 95% CI, 0.79 to 2.30), had lower self-esteem (β, 8.40; 95% CI, 1.68 to 15.12), and were less likely to have current drug abuse or dependence (OR, 0.29; 95% CI, 0.90 to 0.92) or lifetime alcohol abuse or dependence (OR, 0.30; 95% CI, 0.15 to 0.59). A higher proportion of premature adults without neurosensory impairments identified themselves as nonheterosexual (OR, 4.87; 95% CI, 1.01 to 23.69). After exclusion of individuals with neurosensory impairments, differences in employment, social assistance, marital status, and reproduction were no longer significant. Conclusions and relevance: In the fourth decade of life, extremely low-birth-weight survivors achieved similar educational levels and family and partner relationships, and reported fewer risky behaviors compared with controls. However, they had lower levels of employment, income, and self-esteem, and fewer were married and had children. It is therefore essential that these individuals receive necessary support and continued monitoring throughout life.